In case of installing the heating medium utilizing apparatus at an installation site, a pipe connection part is often connected by a ring-type joint. As for the ring-type joint, a brass ring is compressed and deformed by nut and a copper pipe to be sealed, and thus the copper pipe needs to have a hardness being higher than the brass ring.
Patent Literature 1 describes that the copper pipe is processed, thereby producing a joint without using brass. Further, at the time of setting-up the ring-type joint, to avoid water leakage caused by deformation of the copper pipe, some products of copper pipe are made of H material to be used for a local pipe connection part.